Reinforcement Tab

The concrete and steel strengths, bar covers and reinforcement sizes and spacings are defined for the RC wall and base under this tab.

Concrete and Steel Strengths

Concrete grade

Select the concrete grade using either BS or EC definitions, depending on your chosen design code.

For BS design, the concrete tensile strength defaults to 0.25 N/mm², and you may edit this value if required.
For EC design, the concrete tensile strength is calculated automatically by the program.

Reinforcement steel

Select the yield strength of the reinforcing bars from the available options.

Bar Covers

You can specify bar cover independently for:

Wall inner face
Wall outer face
Base and Nib (if present)

Inner face refers to the face of the wall against the retained soil. This is normally the tension face for a cantilever retaining wall.

Reinforcement Layout

In the reinforcement area the bar sizes and spacings are set for the 4 faces of the wall and base, for both the in-plane and longitudinal reinforcement.

In-plane reinforcement (main bending steel)

This is the vertical reinforcement that resists bending of the wall stem.

Longitudinal reinforcement (distribution steel)

This is the distribution reinforcement provided along the length of the wall.

You can decide whether the longitudinal reinforcement is on the inner or outer side of the in-plane main bars.

Automatic Reinforcement Design

The yellow lightning flash button will produce an automatic design for the reinforcement. This option sizes and spaces reinforcement based on the current geometry, loads, and design code settings.

Mesh Bar Sizes Option

Tick Mesh to add intermediate bar diameters commonly used in welded mesh reinforcement to the bar size drop-down list, for example:

5 mm
7 mm
9 mm

Cavity-Filled Masonry Walls

When the wall is to be built from 2 skins of brickwork or blockwork, it is common to infill the cavity with concrete and place reinforcement in it.

To design for this arrangement, tick:

Vertical bars in cavity
Horizontal bars in cavity

You should then edit the cavity inner cover. This cover is measured from the back of the cavity to the main vertical reinforcement. It is not measured from the wall/soil interface, as it is for a solid concrete wall.

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A cavity-filled masonry wall is treated in the same way as a reinforced concrete section:

Reinforcement provides the tension resistance
The masonry outer leaf provides the compression resistance

If a bending check fails, the critical issue may be crushing of the brick or blockwork rather than insufficient reinforcement. In this case, you may need to increase the masonry compressive strength to achieve a satisfactory design.

Reinforced Hollow Block Retaining Walls

MasterKey can also model hollow block retaining walls where the voids are filled with concrete and vertical reinforcement is placed within the hollows.

A common proprietary example is the Stepoc system, where:

Hollow blocks act primarily as permanent formwork
The wall is infilled with concrete
Vertical bars provide main reinforcement
Horizontal reinforcement provides distribution steel

Typical working examples are available in Stepoc Walls . For additional guidance, refer to the technical note on Reinforced Hollow Block Retaining Walls.